With increased consumer demand for mobile broadband and Internet access, recently wireless service providers have implemented cellular carrier aggregation to increase the available bandwidth of wireless wide area networks (WWANs). Furthermore, approaches involving integrating other Radio Access Technologies (RATs) along with the 3GPP Long Term Evolution-Advanced (LTE-A) mobile radio access network are also being developed, so that data traffic could be offload to other RATs and the throughput of transmitting data could be improved thereby. FIG. 1 illustrates a schematic diagram of a communication system including the integration of WWAN and wireless local area network (WLAN). Referring to FIG. 1, the system includes a UE 810 under the coverage of an eNB 820 and an access point (AP) 830. In this system, the AP 830 (which could be compatible with the IEEE 802.11 protocols) would integrated with the eNB 820, and would be connected to Internet 850 through the eNB 820 and the core network 840 behind the eNB 820. As a result, the data transmission between the UE 810 and Internet 850 could be transferred via two paths, the path between the eNB 820 and the UE 810 (e.g., the path P1 using Evolved Universal Terrestrial Radio Access (E-UTRA)), and the path between the AP 830 and the UE 810 (e.g., the path P2 using the 802.11x series of RAT). Also, the eNB 820 would have the ability to control which path could be used to transfer the data. In transmission condition having serious congestion on the path P1, the data from/to the UE 810 could still be successfully transferred by offloading the data to the path P2.
Conventionally, for integrating RATs used in WLANs, e.g., the IEEE 802.11x series of RAT, with WWANs (e.g., RAT used in the LTE-A network), the two access technologies are integrated on the Internet Protocol (IP) layer at the Packet Data Network Gateway (PDN GW, PGW or PDG) inside the core network. Specifically, the integration of WLANs with WWANs can be classified into three categories, namely, no coupling, loose coupling and tight coupling. In the category of no coupling, the WLAN access points are connected to the public internet and the integration point is on the application layer. This is currently the most prevalent way of integration in smart phones or other mobile electronic devices. In loose coupling, a core network entity referred to as ePDG (enhanced Packet Data Network Gateway) is defined in 3GPP S2b architecture to connect operator deployed WLAN access points to the mobile network, and this allows the mobile network operators the ability to route the data traffic through the two networks on the IP layer and to better manage the WLAN access points they deploy. However, progress in this path has been slow and its commercialization seems far away. In other words, based on the conventional loose-coupling architecture, the eNB does not have enough ability to control the radio resource management of LTE and WLAN, so an integration of radio resource management (RRM) of LTE/WLAN is a difficult job. Furthermore, the radio resources from the WLANs and WWANs are not integrated to be efficiently utilized. This deficiency leads to the third category, namely the tight coupling, which is the most efficient and responsive solution but requires more changes in specifications.
The willingness to bring forth the necessary changes is evidenced recently in recent researches, which stated that RAN-level aggregation provides many benefits, such as dynamic allocation of resources based on RF and load conditions, higher aggregate user throughput and system throughput, real-time load balancing and RAN-level seamless handover support. As a result, a novel architecture along with the associated operational procedures that fulfill such goal would be a major issue for those who have skills in the art.